1. Field
The invention relates to a receiving part for receiving a rod for coupling the rod to a bone anchoring element, where the receiving part includes a receiving part body with a channel for receiving the rod and an accommodation space for accommodating a head of the bone anchoring element, and a pressure element with a flexible portion to clamp the head. The flexible portion has a first slit provided in a circumferential direction with respect to a head of the bone anchoring element and a second slit extending from an open end of the pressure element into the first slit, so that a slit ring is integrally formed in the pressure element. Such a receiving part, together with a multitude of different bone anchoring elements, may constitute a modular polyaxial bone anchoring system.
2. Description of Related Art
Various designs of polyaxial bone screws, where a head of a bone anchoring element is clamped from the side to lock an angular position of the bone anchoring element relative to a receiving part, are known.
U.S. Pat. No. 5,672,176 describes a bone screw with a receiving part with a conically shaped seat and a conically shaped pressure element which exerts a pressure onto the head from above and from the side. If the cone angle has a value laying within a specific range self-locking of the pressure element within the receiving part takes place which allows to preliminary lock the head within a receiving part while the rod is still movable in order to allow the adjustment of its position.
U.S. Pat. No. 6,063,090 relates to a device used to connect a longitudinal support to a pedicle screw by an accommodating head having a channel to accommodate the longitudinal support. The pedicle screw and the accommodating head are connected via a conical collet chuck in the accommodating head and by a spherical head on the pedicle screw. The device allows engagement of the pedicle screw in the accommodating head after the pedicle screw has been inserted into the bone.
US 2010/0234902 A1 describes a receiving part for receiving a rod for coupling the rod to a bone anchoring element wherein the receiving part includes a receiving part body and a pressure element arranged therein. The pressure element is movable along a longitudinal axis of the receiving part body from an inserting position insert the head, to a pre-locking position to clamp the head in the receiving part by a pre-stress exerted by the pressure element, to a locking position to lock the head in the receiving part.